Evaluation of Mixed-Mode Fracture Toughness Using Cracked Brazilian Disk

Abstract

Mixed mode fracture toughness for silicon carbide, sialon and mullite was measured using diametral compression tests with a cracked Brazilian disk. Slits introduced by YAG laser in Brazilian disks can be treated as central cracks. The relationships between K1 and K11 for silicon carbide under mixed-mode fracture conditins are consistent with a prediction derived from coplaner energy release rate theory. Experiments on sialon and mullite show that Mode II stress intensity K11C is larger than K1C and Shetty's experimental equation is appropriate for mixed-mode fracture conditions. Observation of fracture surfaces shows that the above differences of fracture conditions depend on the operation of toughning mechanism like grain bridging and grain locking. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.